BIRDS OF CENTRAL AMERICA 251 



neotropical, with certain peculiar endemic forms, the greater 

 number among 'the latter being confined to Mexico arid 

 Guatemala. 



I alluded above to the fact that the family of tortoises, 

 Dermatemydidae, is entirely confined to Central America. 

 The only species of the family (Dermatemys mawi) inhabits 

 precisely that part of Central America which we have reason 

 to believe to be one of its oldest parts, viz., Guatemala and the 

 neighbouring Honduras and Yucatan. Several members of 

 the family formerly lived in North America. They first ap- 

 peared in Cretaceous times, and still inhabited the south- 

 western States during the Eocene Period. It is possible they 

 may then have spread to Guatemala, becoming subsequently 

 extinct in their centre of dispersal.* Another family which 

 I mentioned before (p. 134), the " snapping turtles " (Cheli- 

 dridae), occur in eastern North America from Mexico to 

 Canada. Southward of their range they are found only in 

 Guatemala and Ecuador. We have noted examples of a 

 similar discontinuous range before. Others will be cited in 

 the next chapter. 



More important from a faunistic point of view are such 

 creatures, as for instance the snake-like limbless amphibians, 

 belonging to the family Coeciliidae. They live in moist ground, 

 and lead altogether a burrowing life. Their distribution ought 

 to give us, therefore, some valuable hints as to former changes 

 of land and water. Dr. Sarasin f looks upon this family as a 

 pre-Cretaceous relict, on account of its peculiar discontinuous 

 range, namely India, the Seychelles, east Africa, west Africa, 

 South and Central America. Whether we agree With him or 

 with Dr. Alcock,J who believes that the family wandered 

 along a continuous land surface from India across Africa to 

 northern South America in early Tertiary times, there can be 

 no doubt at all as to these subterranean amphibians being 

 exceedingly ancient. The American home of this circum- 

 tropical family, as Dr. Gadow points out, is South America. 

 No members are known from the West Indies or the Galapagos 



* Hay, 0. P., " On Fossil Turtles," p. 32. 



t Sarasin, F., " Geschichte d. Tierwelt von Ceylon," pp. 74 76. 



t Alcock, A., " Description of Apodous Amphibian," p. 270. 



Gadow, H., " Distribution of Mexican Amphibians," pp. 199 200. 



